WHO- and UNEP-Coordinated Exposure Studies 2000–2019: Findings of Polybrominated Substances (PBDE, HBCDD, PBB 153, PBDD/PBDF)

Abstract The concentrations of a number of polybrominated substances were determined in pooled human milk samples collected from up to 80 countries from all the United Nations Regional Groups. The samples were taken from one or more of the five exposure studies on persistent organic pollutants coordinated by the World Health Organization and the United Nations Environment Programme between 2000 and 2019. Large differences in levels were found for polybrominated diphenyl ethers (PBDE). The concentration of the sum of 6 PBDE congeners (∑PBDE 6 : BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183) of 135 pooled samples from 80 countries was in the range between 0.3 and 352 ng/g lipid (median 1.6 ng/g lipid). The highest concentrations were detected in the Western European and Others Group (including Australia, Israel, New Zealand, and the USA) in 2003. Time trends were assessed for 36 countries with repeated participation. Rates of decrease tend to fluctuate at near background levels; but at higher levels, a decreasing trend was observed for nearly all countries. Deca-BDE (BDE-209) contributed on average about 13% to ∑PBDE 7 (sum of ∑PBDE 6 plus BDE-209). The contribution of the octa-brominated diphenyl ether (octa-BDE) BDE-197 and nona-BDEs-206, -207, and -208 to the sum of 25 PBDE was in the range of the six recommended analytes and BDE-209. Therefore, their addition to the list of recommended analytes should be considered. The α-HBCDD levels of 102 pooled samples from 72 countries collected between 2006 and 2019 ranged between <0.1 and 15 ng/g lipid (median: 0.5 ng/g lipid). β-HBCDD and γ-HBCDD were in nearly all samples below the limit of quantification (LOQ for 90% of the samples: <0.1 ng/g lipid) or around the LOQ (max: 0.8 ng/g lipid). Thus, it can be concluded that α-HBCD is the predominant stereoisomer in human milk. Hexabromobiphenyl (PBB 153) was below the limit of quantification (0.5 ng/g lipid) in 106 of 110 pooled samples from 69 countries. In four samples, low concentrations of between 1.0 and 1.7 ng/g lipid were found. In addition to these chemicals listed by the Stockholm Convention on Persistent Organic Pollutants, in 38 pooled samples from 28 countries concentrations of polybrominated dibenzodioxins and -furans (PBDD/PBDF) were determined to assess their contribution to the overall sum of WHO 2005 toxic equivalents (TEQ) with polychlorinated dibenzo- p -dioxins (PCDD) and polychlorinated dibenzofurans (PCDF). PBDD and PBDF provided on average about 10% to the overall TEQ calculated as sum of WHO-PCDD/PCDF-TEQ and WHO-PBDD/PBDF-TEQ, when assuming the same toxic equivalency factors for brominated congeners as assigned to their chlorinated analogs. No correlations between PCDD/PCDF and PBDD/PBDF, or PBDD/PBDF and PBDE were found.